Apparatus for selective electroplating of sheets

ABSTRACT

Apparatus for selectively electroplating discrete areas on a sheet employs a plurality of dams to conduct plating solution to and from the sheet. A plurality of resilient seals bearing against the material to be plated seal preselected surface portions of the sheet into contact with the fluid zone and other portions out of such contact, the seals also forming a part of a conduit normal to the preselected portions. A pump pumps plating solution through the fluid zone so as to promote turbulence adjacent the preselected surface portions.

July 1 0, 1973 osows v ET AL 3,745,105

APPARATUS FOR SELECTIVE ELECTROPLATING OF SHEETS Filed Nov. 18, 1970 2Sheets-Sheet 1 John G. Cunniff Robert T. Groom Zia/{alum ATTORNEYS vJuly 10, 1973 1.. N. KOSOWSKY ET AL 3,745,105

APPARATUS FOR SELECTIVE ELECTROPLATING OF SHEETS Filed Nov. 18, 1970 7 2Sheets-Sheet Fig. 3

, v wig 38 r 7 1, 33, o o o 3 i ,45

o o o A j I 3 o 0 0 o Vr o o o :44 4 L lL-gi i 1 l I 4| j i g u 7 f Al/t/ 1/ 1 1/! 3'8 v 4 44 44 46 Fig.6 W

mw D n mu 49 52 Z3553. 1 [:22 F 5 unmmmnnnmmmnu WWW :qN\'\/(ENTOI:SWQMQE max,

Robert T. Groom Jan/u: W7C 25 614114 ATTORNEYS John G. Cunniff U.S. (:1.204-224 R 3,745,105 APPARATUS FOR SELECTIVE ELECTROPLATING OF SHEETS LeoN. Kosowsky, Sharon, and Curtis N. Love oy, Walpole, Mass, and John G.Cunnitf, Foster, and Robert T. Groom, Warwick, R.I., assignors to AuricCorporation, Newark, NJ.

Filed Nov. 18, 1970, Ser. No. 90,632 Int. Cl. 1323p 1/02; Btllk 3/00 13Claims ABSTRACT OF THE DISCLOSURE Apparatus for selectivelyelectroplating discrete areas on a sheet employs a plurality of dams toconduct plating solution to and from the sheet. A plurality of resilientseals bearing against the material to be plated seal preselected surfaceportions of the sheet into contact with the fluid zone and otherportions out of such contact, the seals also forming a part of a conduitnormal to the preselected portions. A pump pumps plating solutionthrough the fluid zone so as to promote turbulence adjacent thepreselected surface portions.

BACKGROUND OF THE INVENTION (A) Field of the invention This inventionrelates to apparatus and process for uniformly electroplating aplurality of discrete areas on a metallic substrate while maintainingthe rest of the substrate out of contact with the electroplating bath.

(B) The prior art In many electroplating operations, e.g. operationswherein microcircuits are electroplated with gold, there is a need tominimize the amount of expensive metal utilized by closely restrictingits deposition to only those surface areas where its presence isessential. It is desirable, however, that such selective deposition ofthe metal be achieved without resorting to procedures which greatlyrestrict the production rate of an electroplating facility or whichgreatly increase the handling costs of the items being electroplated.

It has been known to use organic coatings to mask those areas ofmetallic substrates on which electroplating is not required and therebyavoid those areas being electroplated. After the electroplating step isfinished, the masking material is removed, leaving the discreteelectroplated zones. Obviously such a process requires expensive coatingand stripping steps. Such steps add to the cost of the electroplatingoperation and also increase the probability that some of the workproduct will have to be scrapped because of damage incurred during themanufacturing operations.

Other suggestions have been made for electroplating small selectedareas, but these suggestions have been limited to small-scale,repair-type operations wherein the rigorous requirements of high-rate orcontinuous manufacture need not be considered. Thus, for example,Ehrhart, in US. Pat. No. 3,071,521, discloses a single grommet-sealedchamber for use in repairing printed-circuits. Swanson, in U.S. Pat. No.2,698,832, discloses a somewhat similar device utilizing a reservoir foran electroplating solution adapted to empty, by gravity flow, into areceptical for receiving the solution. Neither of these mventions hassuggested a way whereby a large number of discrete areas can be carriedout at the same time and at optimum current densities. Indeed, neitherinventor, in solving his own particular problem, has been faced withproblems as complex as those involved in the electroplating of aplurality of discrete areas on the same electroplating apparatus.

United States Patent O 3,745,105 Patented July 10, 1973 Allelectrodeposited metals have crystalline structures which manifestthemselves in the physical properties and appearance of the platedmetal. In order to achieve plated deposits of suitable properties, it isnecessary to control the current density at which the plating is carriedout. Excessive current densities will result in deposits of poorquality. However, current densities which are too low will result inexcessively long plating cycles and markedly reduce the production rateof the plating operations. It has been a particular problem inconstructing apparatus suitable for electroplating of a large number ofselected areas on a single extensive substrate to assure a suitablyconcentrated electroplating solution at each of the discrete areas beingplated to enable plating at desired current densities.

In commercial work, preparation of surfaces for plating is often asimportant as the electroplating step itself. This is especially so inelectroplating surfaces for use in micro-circuit components. Thus,special care should be exercised in the construction of apparatus toassure that the surfaces to be electroplated are processed withoutcontacting machine parts or by an operators hands. This requirement hasincreased the difficulty of providing suitable apparatus for theelectroplating of a large number of selected areas on a single, butextensive, substrate.

Ramirez et al., in US. Pat. 2,974,097 disclose means for continuouslyplating areas along the edges of a continuous strip. It should be noted,however, that the area being electroplated is a continuous area, not aplurality of small areas. Thus, the problem of solution distribution ismuch simpler than the one encountered by the instant inventors.

SUMMARY OF THE INVENTION Therefore it is an object of the instantinvention to provide apparatus which can quickly and conveniently effectthe uniform and simultaneous electroplating of a large number ofpre-selected discrete surface zones of a sheet.

Still another object of the invention is to provide an paratus havingcompact means for maintaining the desired concentration of, andagitation of, the electroplating solution.

Another object of the invention is to provide a novel process forelectroplating pre-selected discrete surfaces zones on a sheet.

Other objects of the invention will be obvious to those skilled in theart on reading the application.

The above objects have been economically and conveniently achieved byconstruction of electroplating apparatus which provides for themaintenance of suitably high cation contents in the immediate vicinityof all of the discrete surfaces being electroplated and which issufficiently versatile that surfaces of various sizes and shapes canbeselected for electroplating without major modification of the apparatus.

The high cation contents are maintained, even at current densities of15-25 amps per foot and above in acid gold plating, by providing such ahigh flow of fluid proximate the surfaces being plated that excellentagitation is achieved. The ability to use the apparatus at high currentdensities markedly reduces the time which would otherwlse be required toobtain platings of good quality to be achieved.

Because the total flow of electroplating solution would be, in thepractice of the present invention, much greater than that required toprovide sufiicient metal to the surface being plated, it is sometimespossible to include inert fluid-fillers (such as gases, immiscibleliquids, and slurried solids) in the fluid pumped through the apparatus.

solution.

A particular advantage of the invention is the fact that it can beutilized to plate surfaces which are perforated or surfaces which arenot perforated. A turbulence-promoting fluid path is utilized tofacilitate the plating of the latter surfaces with theturbulence-promoting means advantageously being a sudden enlargement, asudden contraction, a change in direction in the fluid path, or acombination of these. In order that such a turbulence-promoting meanshave the desired effect at the surface being electroplated, it isdesirable that it be a distance from the non-perforated surface beingelectroplated of less than about 0.5 diameter of the conduit leadingfrom the turbulence-promoting means to the surface being electroplated.

When a perforated sheet is used so that the electroplating solutionpasses through the sheet to effect plating on both sides thereof, thesheet itself usually acts as an eificient turbulence-promoting device ifthe perforations or apertures therein generally extend over the entirearea to be electroplated.

ILLUSTRA'TIVE EMBODIMENT OF THE INVENTION In this application andaccompanying drawings We have shown and described a preferred embodimentof our invention and have suggested various alternatives andmodifications thereof, but it is to be understood that these are notintended to be exhaustive and that other changes and modifications canbe made within the scope of the invention. These suggestions herein areselected and included for purposes of illustration in order that othersskilled in the art will more fully understand the invention and theprinciples thereof and will be able to modify it and embody it in avariety of forms, each as may be best suited in the condition of aparticular case.

In the drawings:

FIG. 1 is a schematic elevation showing the general configuration of theelectroplating apparatus according to the invention.

FIG. 2 is a plan view of the support assembly on which objects to beelectroplated rest.

FIG. 3 is a plan view, partly in section, of the flowdistributingchamber.

FIG. 4 is a section taken along lines 4-4 of FIG. 3.

FIG. 5 is a plan view segment of a workpiece which has beenelectroplated at selected, non-perforated portions of the surfacesthereof.

FIG. 6 is a plan view of a segment of a workpiece which has beenelectroplated at selected, perforated portions of the surface thereof.

Referring to FIG. 1, it is seen that a selective electroplatingapparatus 10 is mounted on a hydraulic-press 12 so that an upper member13 comprising flow-distributing chamber 14 can be moved into contactwith lower support member 16. The press is shown in its open position.Each of upper member 13 and lower member 16 comprise a series ofgrommets 18 and 19 mounted, respectively, on the opposing faces thereof.These grommets, when in register with one another, are adapted to bearagainst a sheet to be electroplated and to form seal means to restrictthe flow of electroplating solution to those surfaces of sheet which aredefined by an aperture in the grommet.

When members 13 and 16 are brought together so that the upper grommetsand lower grommets sealingly contact each other, electroplating solutionof the type known in the art and stored in reservoir 20 is pumped viapump 22 and pipe 24 into flow-distributing chamber 14. The solution isthen conducted (through a liquid zone defined by flow paths more clearlyshown in'FIGS. 2 through 5) back into a chamber 26 in lower member 16,thence through return conduit 28 and back to reservoir 20.

FIG. 2 illustrates the faceplate 32 of lower support member 16 and theplacement of grommets 19 on the surface thereof. Some of grommets 19 arenot shown to more clearly show apertures 30 in lower face plate 32.

4 Apertures 30 are vertical conduits leading into chamber 26.

Around the area of faceplate 32 on which grommets 19 are adhesivelypositioned, is a semicircular drain groove 36 which cooperates with asimilar groove 38 in upper face plate 40 (see FIG. 3) to form aperimeter drain 34 most clearly shown in FIG. 4. This perimeter drain 34provides a flow path whereby excess electroplating solution can becarried to large vertical conduits 42 and thence downwardly into chamber26, conduit 28 and reservoir 20.

FIGS. 3 and 4 best illustrate the flow paths by which the flow ofelectroplating solution is distributed to the surfaces to beelectroplated and continuously replenished in the vicinity of saidsurfaces.

FIG. 3 is a bottom view of the upper member 13 showing a face plate 40on which are mounted grommets 18.

Grommets 18 surround vertical conduits 44 which, roughly, correspond toapertures 30 in lower face plate 32. These conduits 44 are connected viasmaller lateral conduits 45 to transverse drain channels 46. Lateralconduits 45 and drain channels 46 provide means for a continuoushigh-rate flow of electroplating solution to be returned to upper draingroove 38 and perimeter drain 34.

FIG. 4 shows how lateral conduits 45 are positioned proximate thegrommets 18 so that the flow there into creates sufficient turbulenceand mixing in the terminal portion of conduits 44 to allow the properconcentration of electroplating solution to be maintained even whenrelatively high current densities are utilized. This factor is ofparticular importance when the selected portions of the sheet to beelectroplated are not perforated to allow flow of solution therethrough.

Also seen in FIG. 4 is anode grid 60 which is mounted in upper member 13just above upper face plate 40. The anode is submerged in electroplatingsolution during the plating operation. The cathode comprises twometallic strips in the form of spring 62 which are mounted on uppermember 13 and positioned to contact (a conductive sheet, e.g., sheet 49shown in FIG. 4 to be sealed between grommets 18 and 19) and therebyincorporate as a cathode the conductive sheet to be electroplated.

FIG. 5 shows a plan view of a portion of a typical metallic sheet 49which is electroplated only in non-perforated areas 50 which correspondto the size of the aperture in the grommet which seals against area 50.

FIG. 6 shows a plan view of a portion of a typical metallic sheet 52which is electroplated only in perforated areas 54.

In one typical operating procedure, a pump with a nominal capacity of350 gallons per hour is used to supply fluid to the illustratedapparatus wherein the vertical conduit 44 is -inch in diameter, theconduits 45 are %;-inch in diameter, and the large drain holes 42 inbottom plate are %-inch in diameter. The inside diameter of the lowergrommet 19 and vertical conduit 30 therebeneath are -inch.

An air-drying neoprene-based cement of the type known in the artprovides a suitable adhesive for use in attaching the grommets to theface plates of the apparatus. The face plates themselves are suitablyformed of metal or plastic materials. The effective area of the anode isusually at least twice the effective area of the cathode.

It will thus be seen that the objects set forth above among those madeapparent from the preceding description are eificiently attained and,since certain changes may be made in the above product without departingfrom the scope of the invention, it is intended that all mattercontained in the above description shall be interpreted as illustrativeand not in a limiting sene. It is also to be understood that thefollowing claims are intended to cover all of the generic and specificfeatures of the invention herein described, and all statements of thescope of the invention which, as a matter of language, might be said tofall. therebetween.

What is claimed is:

1. Apparatus for use in selectively and simultaneously electroplating aplurality of discrete areas on sheet material said apparatus comprising(A) a fluid zone forming means to conduct electroplating solution to andfrom said sheet material;

(B) a sealing means adapted for hearing against a material to beelectroplated and comprising a plurality of resilient seals adapted forsealing pre-selected surface portions of said sheet into contact withsaid fluid zone and other portions of said sheet out of contact withsaid fluid zone; said seals forming par-t of a conduit which is normalto said preselected portions;

(C) means for pumping electroplating solution through said fluid zone,said pumping means being of such capacity that it forms means to agitateelectroplating solution on pumping said solution throughturbulencepromoting means positioned proximate said seal means andadapted to promote turbulence adjacent said preselected portions of saidsheet.

2. Apparatus as defined in claim 1 wherein said seal means are gasketsadhesively and removably, attached to said apparatus, hence forminginterchangeable means to define the size and shape of said pre-selectedareas.

3. Apparatus as defined in claim 1 wherein said fluid zone comprises afluid path through apertures formed by said resilient seals adapted toseal pro-selected portions on opposing sides of said sheet.

4. Apparatus as defined in claim 1 wherein said fluid zone does notcomprise a fluid path through each said preselected portion of saidsheet.

5. Apparatus as defined in claim 1 (1) wherein said resilient seals aregaskets having apertures, the cross sec.- tion of which are adapted todefine said pre-selected portions of said sheet and (2) wherein aflow-distributing member comprising conduits leading to said aperturesand a system of channels leading from each said conduit at a positionadjacent said gaskets, said system of channels, forming means to assureflow-induced agitation of liquid in said gasket apertures.

6. Apparatus as defined in claim 5 wherein said channels leading frompoints in said conduit adjacent said gaskets terminate at a peripheraldrain surrounding and defining the outer boundary of said fluid zone.

7. Apparatus as defined in claim 6 wherein said peripheral drain isformed by said flow-distributing member and a support member.

8. Apparatus as defined in claim 7 wherein said support member comprisesconduit means to carry said fluid out of the apparatus.

9. Apparatus as defined in claim 5 wherein said gaskets on saidflow-distributing member and gaskets on a support member are adapted tohold said sheet and the cross-section of an aperture in said gasketsforms means to define areas of said sheet to be electroplated.

10. Apparatus as defined in claim 4 wherein said sheet is a cathode andan anode is positioned in a chamber forming part of said fluid zone insaid flow-distributng member.

11. Apparatus as defined in claim 5 comprising electrical connections toadapt said sheet as a cathode and (2) an anode positioned in a chamberforming part of said fluid zone in said flow-distributing member.

12. Apparatus as defined in claim 1 wherein said cathode contactselectrical contacts formed as springs which bias said flow-distributingmember against said sheet and are positioned within the space defined bythe exterior walls of the gaskets and outside said fluid zone.

13. Apparatus as defined in claim 5 wherein said channels branch fromsaid conduit at a distance of less than about 0.5 diameter of saidconduit from an edge of said gaskets adapted to bear against a sheet tobe processed.

References Cited UNITED STATES PATENTS 2,721,839 10/119 Taylor 204 291RX 3,644,181 2/1972 Donaldson 204-224 x 3,658,684 4/1912 Sickels 204-424X 2,895,814 7/1959 Clark 204-224 x 3,317,410 5/1967 CI'Oll et al 204-239X FOREIGN PATENTS 1,098,182 1/1968 Great Britain 204-15 760,016 10/1956Great Britain 204-224 JOHN H. MACK, Primary Examiner D. R. VALENTINE,Assistant Examiner US. Cl. X.R.

